Conductive metal ink composition and method for forming a conductive pattern

ABSTRACT

The present invention relates to a conductive metal ink composition which is properly applied for roll-printing process to form conductive pattern with improved conductivity, and the method of preparing a conductive pattern using the same. 
     The conductive metal ink composition comprises a conductive metal powder; an organic silver complex where an organic ligand including amine group and hydroxyl group binds with a silver (Ag) salt of aliphatic carboxylic acid; a non-aqueous solvent comprising a first non-aqueous solvent having a vapor pressure of 3 torr or lower at 25° C. and a second non-aqueous solvent having a vapor pressure of higher than 3 torr at 25° C.; and a coatability improving polymer.

This application is a National Stage Entry of International ApplicationNo. PCT/KR2010/005651, filed Aug. 24, 2010, and claims the benefit ofKorean Patent Application Nos. 10-2009-0079361, filed on Aug. 26, 2009,and 10-2010-0081974, filed on Aug. 24, 2010, which are herebyincorporated by reference for all purposes as if fully set forth herein.

1. Technical Field

The present invention provides a conductive metal ink composition and amethod for forming a conductive pattern. More specifically, the presentinvention provides the conductive metal ink composition which isproperly applied for roll-printing process to form conductive patternwith improved conductivity, and the method of preparing a conductivepattern using the same.

2. Background Art

Recently, various flat panel display devices have been used widely. Tomanufacture the flat panel display device, many conductive patterns suchas electrode, wiring, and EMI-shield filter are formed on a substrate,usually by photolithography.

However, the pattern formation by photolithography requires many stepsof coating of photosensitive material, exposing, developing, etching andetc., thereby making the entire process be complex and expensive.

Therefore, there are increasing focuses on the method of preparing theconductive pattern using inkjet printing method, roll printing methodand etc. Particularly, the roll printing method attracts more attention,because it has an advantage in making the fine conductive pattern whichis very difficult to form by using the inkjet printing method. In orderthat good conductive pattern is obtained by using the roll printingmethod, the conductive ink composition to be used must have properproperties such as a low initial viscosity to be well coated on theroller, and a property being satisfactorily transferred to the substratein a desired pattern.

However, a conductive ink composition which is satisfactory enough toform a fine conductive pattern by the roll printing method cannot bedeveloped as yet. Moreover, in case that the previously-developedconductive ink composition having a low initial viscosity is used, theconductivity of conductive pattern is not sufficient enough. Thus, thereis still need for conductive ink composition with excellent propertiesbeing capable of forming fine conductive pattern.

DISCLOSURE Technical Problem

The present invention provides a conductive metal ink composition whichis properly applied for a roll printing process to form conductivepattern with improved conductivity, and a method of preparing aconductive pattern.

In addition, the present invention provides a method of preparing aconductive pattern by using the conductive metal ink composition.

Technical Solution

The present invention provides a conductive metal ink compositioncomprising a conductive metal powder; an organic silver complex where anorganic ligand including amine group and hydroxyl group binds with asilver (Ag) salt of aliphatic carboxylic acid; a non-aqueous solventcomprising a first non-aqueous solvent having a vapor pressure of 3 torror lower at 25° C. and a second non-aqueous solvent having a vaporpressure of higher than 3 torr at 25° C.; and a coatability improvingpolymer.

The present invention provides also a method of forming a conductivepattern, comprising the steps of:

coating a conductive metal ink composition on a roller;

forming a pattern of the ink composition corresponding to the conductivepattern on the roller, by contacting the roller with a printing clichéwhich has intaglio pattern corresponding to the conductive pattern;

transferring the pattern of the ink composition on the roller onto asubstrate; and sintering the transferred pattern on the substrate.

The conductive metal ink composition and the method of preparingconductive pattern using the same according to the present inventionwill be described in more detail.

In accordance with an embodiment, there is provided a conductive metalink composition comprising a conductive metal powder; an organic silvercomplex where an organic ligand including amine group and hydroxyl groupbinds with a silver (Ag) salt of aliphatic carboxylic acid; anon-aqueous solvent comprising a first non-aqueous solvent having avapor pressure of 3 torr or lower at 25° C. and a second non-aqueoussolvent having a vapor pressure of higher than 3 torr at 25° C.; and acoatability improving polymer.

The conductive metal ink composition includes as a media the firstnon-aqueous solvent and the second non-aqueous solvent, which havedifferent vapor pressure at room temperature. The first and the secondnon-aqueous solvents show different volatile properties due to thedifferent vapor pressure, and particularly, the second non-aqueoussolvent has higher vapor pressure and volatile property than those ofthe first non-aqueous solvent at room temperature. Therefore, theconductive metal ink composition including the first and the secondnon-aqueous solvents shows low viscosity and maintains uniformcomposition in the media including the including the first and thesecond non-aqueous solvents for a storage time, until it is coated onthe roller in the roll printing process. Thus, the conductive metal inkcomposition can be easily coated on the roller uniformly.

In addition, when the conductive metal ink composition is exposed toair, the second non-aqueous solvent begins to volatilize shortly afterthe exposure due to its high volatility, and thus the viscosity of thecomposition gets higher sharply in several minutes. The ink compositioncoated on the roller can be easily patterned as the desired patterningshape. In addition, even after patterning, the ink composition cannotrun down from the roller, and can maintain the good pattern shape.

Accordingly, if the roll printing is performed by using the conductivemetal ink composition, the desired pattern can be transferred to thesubstrate with maintaining the good pattern shape and fine conductivepattern can be satisfactorily formed.

The conductive metal ink composition comprises an organic silver complexwhich is formed by binding an organic ligand including amine group andhydroxyl group to a silver (Ag) salt of aliphatic carboxylic acid. Theexample of organic silver complex is one described in KR 2008-0029826A,and the organic silver complex has a high solubility in solvent,maintains liquid-phase at room temperature, and shows an excellentstability in the ink composition without additional dispersing agent.That is, the organic silver complex can act as a kind of medium, andincludes silver in itself. Inclusion of the organic silver complex inthe conductive metal ink composition make it possible to decrease anamount of non-aqueous solvent in the ink composition and to contain moreamount of conductive metal component such as silver (Ag) or otherconductive powder. Therefore, the conductive metal ink compositionincludes the organic silver complex together with the conductive metalpowder, thereby causing the improved conductivity of the conductivemetal ink composition.

Hereinafter, each component of the conductive metal ink compositionaccording to an embodiment of the present invention will be described indetail.

Firstly, the conductive metal powder is contained in the ink compositionas a basic component to give the conductivity. The conductive metalpowder can be any metal powder with electrical conductivity and forexamples, includes at least one selected from the group consisting ofsilver (Ag), copper(Cu), gold(Au), chrome(Cr), aluminum(Al),tungsten(W), zinc(Zn), nickel(Ni), iron(Fe), platinum(Pt) and lead(Pb).In order that the conductive pattern prepared from the ink compositionshows excellent and uniform conductivity due to the uniform distributionof the metal powder, the metal powder have an average particle diameterof nano-scale. For example, the average diameter of the metal powder canbe about 1 to 100 nm, preferably about 5 to 70 nm, or more preferablyabout 10 to 50 nm.

The conductive metal powder can be contained at an amount of about 15 to30 wt %, preferably about 20 to 30 wt %, or more preferably about 23 to30 wt %, on the basis of total weight of other components in thecomposition except for the organic silver complex, where the totalweight of other components are sum of the weights of conductive metalpowder, the first non-aqueous solvent, the second non-aqueous solvent,the coatability improving polymer, and optionally the surfactant. If theamount of conductive metal powder is excessively small, the conductivityof conductive pattern formed from ink composition may be not sufficient.On the other hand, if it exceeds the amount, the poor property of theconductive pattern or the non-uniform coating of the composition can beobtained due to the poor distribution of the metal powder in the inkcomposition.

The conductive metal ink composition includes the first non-aqueoussolvent and the second non-aqueous solvent. The first non-aqueoussolvent has a vapor pressure of 3 torr or lower at 25° C. and arelatively low volatility, and acts a dispersing agent before sintering.

The first non-aqueous solvent can be any solvent having a vapor pressureof 3 torr or lower at 25° C., and the examples of first non-aqueoussolvent are at least one or two volatile solvents selected from thegroup consisting of alcohol-based solvent, glycol-based solvent,polyol-based solvent, glycol ether-based solvent, glycol etherester-based solvent, ketone-based solvent, hydrocarbon-based solvent,lactate-based solvent, ester-based solvent, aprotic sulfoxide-basedsolvent, and nitrile-based solvent, which have a vapor pressure of 3torr or lower at 25° C. The specific examples of the first non-aqueoussolvent are ethylene glycol, propylene glycol, glycerol, propyleneglycol propylether, ethylene glycol monophenylether, ethylene glycolmonoisopropylether, propyleneglycol monobutylether, diethylene glycolmonobutylether, diethylene glycol monobutylether acetate, diethyleneglycol ethylether, N-methylpyrrolidone, hexadecan, pentadecan,tetradecan, tridecan, dodecan, undecan, decan, DMSO, acetonitrile andbutyl cellosolve.

The second non-aqueous solvent is a highly-volatile solvent having avapor pressure of more than 3 torr at 25° C. As described above, thesecond non-aqueous solvent maintains a low viscosity and a goodcoatability on the roller together with the first non-aqueous solventbefore coating of the ink composition, it is removed by evaporation toincrease the viscosity of ink composition, and makes the pattern beformed and maintained on the roller.

The second non-aqueous solvent can be any solvent having a vaporpressure of higher than 3 torr and the examples are at least one or twovolatile solvents selected from the group consisting of alcohol-basedsolvent, glycol ether-based solvent, glycol ether ester-based solvent,ketone-based solvent, hydrocarbon-based solvent, lactate-based solvent,ester-based solvent, aprotic sulfoxide-based solvent, and nitrile-basedsolvent which have a vapor pressure of higher than 3 torr at 25° C. Thespecific examples are at least one or two volatile solvents selectedfrom the group consisting of methanol, ethanol, propanol, isopropanol,n-butanol, t-butanol, pentanol, hexanol, nonan octan, heptan, hexan,acetone, methylethylketone, methylisobutylketone, methyl cellosolve,ethylcellosolve, ethylene glycol dimethylether, ethylene glycoldiethylether, propyleneglycol methylether acetate, chloroform, methylenechloride, 1,2-dichloroethan, 1,1,1-trichloroethan, 1,1,2-trichloroethan,1,1,2-trichloroethene, cyclohexan, tetrahydrofuran, benzene, toluene andxylene.

Each first non-aqueous solvent and the second non-aqueous solvent can becontained at an amount of about 5 to 70 wt % and about 10 to 74 wt %,preferably about 20 to 50 wt % and about 25 to 55 wt %, and morepreferably about 25 to 48 wt % and about 30 to 53 wt %, on the basis oftotal weight of other components in the composition except for theorganic silver complex where the total weight of other components aresum of the weights of conductive metal powder, the first non-aqueoussolvent, the second non-aqueous solvent, the coatability improvingpolymer, and optionally the surfactant

When the amount of first non-aqueous solvent is small, or when theamount of second non-aqueous solvent is excessively large, the dryingrate of ink composition becomes high after coating on the roller,thereby making the transfer be difficult. On the other hand, when theamount of the first non-aqueous solvent is larger than the ranges, orwhen the amount of the second non-aqueous solvent is excessively small,the low drying rate makes the entire process be delayed and makes itdifficult to coat the ink composition.

The conductive metal ink composition includes the coatability improvingpolymer. The coatability improving agent acts as a binder in the inkcomposition and provides the adhesiveness, resulting in satisfactorycoating and transferring of the ink composition in the preparationprocess of conductive pattern.

The coatability improving agent can be at least an adhesive polymerselected from the group consisting of epoxy-based polymer, phenol-basedpolymer, alcohol-based polymer. Examples of the epoxy-based polymerincludes bisphenol A epoxy polymer, bisphenol F epoxy polymer, novolacepoxy resin, flame retarded epoxy resin such as bromo-epoxy resin,alicyclic epoxy polymer, rubber-modified epoxy resin, aliphaticpolyglycidyl epoxy resin and glycidylamine epoxy polymer. The examplesof phenol-based polymer are novolac phenol resin and resole phenolresin, and the examples of -based polymer are cellulosic polymer,polyvinylalcohol and ethylene vinyl alcohol. Besides, the examples ofcoatability improving polymer are ethylenevinylacetate, rosin-basedresin, styrene-butadiene-styrene-based polymer, polyester-based polymerand etc.

Any material of the examples which are widely known orcommercially-available materials, can be used as a coatability improvingagent, and various polymers as well as the specific examples which hasbeen used in the conductive ink composition can be used as a coatabilityimproving agent.

Because the ink composition includes the coatability improving agent,the composition shows an excellent coatability on the roller, and a goodtransferring property to the substrate. Therefore, the ink compositioncan be applied for the roll printing method to form the fine conductivepattern.

The coatability improving agent can be contained in the ink compositionat an amount of about 0.1 to 5 wt %, preferably about 1 to 4 wt %, ormore preferably about 2 to 3 wt %, on the basis of total weight of othercomponents in the composition except for the organic silver complex,where the total weight of other components are sum of the weights ofconductive metal powder, the first non-aqueous solvent, the secondnon-aqueous solvent, the coatability improving polymer, and optionallythe surfactant. If the amount is excessively small, the coatability andtransferring property of ink composition are not sufficient. If theamount is excessively large, the conductive pattern of the inkcomposition cannot show sufficient conductivity.

Besides the components as described above, the conductive metal inkcomposition includes an organic silver complex where an organic ligandincluding amine group and hydroxyl group binds with a silver (Ag) saltof aliphatic carboxylic acid. The organic silver complex is prepared bybinding an organic ligand selected from the group consisting of primary,secondary, tertiary and quaternary amines substituted with an alcoholgroup, with silver salt of aliphatic carboxylic acids. In addition, thesilver salt of aliphatic carboxylic acid is selected from the groupconsisting of silver salts of primary or secondary fatty acid having C2to C20. An equivalent ratio of the organic ligand to aliphaticcarboxylic acid is 2:1 in organic silver complex.

The organic silver complex shows a low crystallinity due to the chemicalcomplex type and an excellent solubility in solvent, resulting in theliquid-phase at room temperature. Since the organic silver complex canacts as a liquid-phase medium by itself, it reduces the amount ofmedium, namely non-aqueous solvent and increases the amount ofconductive metal component such as conductive metal powder or silverincluded in the organic silver complex. Thus, the ink composition isapplied for the roll printing method to form fine conductive patternwith an improved conductivity.

In addition, the organic silver complex includes the organic ligand andthe silver salt of aliphatic carboxylic acid at an equivalent ratio ofthe organic ligand to the silver salt of aliphatic carboxylic acid of2:1, which means two hydroxyl groups in a molecule, and thus shows highviscosity, for example, 50 to 2,000 cPs at room temperature (about 25°C.). The organic silver complex can function as a medium in the inkcomposition and thus, the ink composition can maintain excellentdistribution stability even at low amount of non-aqueous solvent.

Because the ink composition includes the organic silver complex, higherdensity of conductive metal component and the conductive pattern withgood conductivity can be obtained.

The examples of organic silver complexes which are disclosed in KR2008-0029826A can be used for the ink composition of the presentinvention. As described in KR 2008-0029826A, the organic silver complexcan be prepared by reacting the organic ligand with the silver salts ofaliphatic carboxylic acid and the examples of solvent include methanol,terpineol, butyl carbitol acetate and etc.

The organic silver complex can be contained at an amount of about 0.1 to5 parts by weight, preferably about 1 to 5 parts by weight, or morepreferably about 3 to 5 parts by weight, with respect to 100 parts byweight of the conductive metal powder contained in the ink composition.If the amount gets small, the conductivity of the conductive patternprepared from the ink composition is not sufficient. If the organicsilver complex is contained excessively, the process is difficult toperform due to the increased viscosity of ink composition.

Besides the components in the ink composition, the composition canfurther include a surfactant. The surfactant contained in the inkcomposition prevents dewetting phenomenon and pinhole occurring, whenthe ink composition is coated on the roller. As a result, the inkcomposition can be coated favorably on the roller, so as to form thefine conductive pattern.

The silicon-based surfactant which has been used commonly in theconductive metal ink composition, for example, polydimethyl siloxane canbe used as a surfactant, and other kinds of surfactants can be used forthe present invention without any limitation.

The surfactant can be used at an amount of about 0.01 to 4 wt %,preferably about 1 to 4 wt %, or more preferably about 2 to 3 wt %, onthe basis of total weight of other components in the composition exceptfor the organic silver complex, where the total weight of othercomponents are sum of the weights of conductive metal powder, the firstnon-aqueous solvent, the second non-aqueous solvent, the coatabilityimproving polymer, and optionally the surfactant. Because the surfactantis contained in the ink composition in the ranges, the ink compositioncan be easily coated on the roller.

The conductive metal ink composition of the present invention has aninitial viscosity of about 20 cPs or lower, preferably about 7 cPs orlower, or more preferably about 5 cPs or lower. Hereinafter, the term,“initial viscosity” means the viscosity while the ink composition isprepared initially and is coated on the roller. More specifically, theterm, “initial viscosity” can means the viscosity of the ink compositionthat is stored after the preparation until the ink composition iscoated. Namely, the viscosity is referred to the viscosity of the inkcomposition, before the ink composition is exposed to air and is coatedon the roller. The conductive metal ink composition has such a lowviscosity due to the inclusion of the first non-aqueous solvent and thesecond non-aqueous solvent, resulting in excellent coatability on theroller. After the ink composition is coated on the roller, the viscositybecomes high due to the evaporation of the second non-aqueous solventwith high volatility, thereby forming and maintaining the good patternon the roller and transferring to the substrate.

If the initial viscosity is excessively high, it is difficult to controlthe pumping pressure and to obtain the good coatability on the roller,when the ink composition is coated on the roller. The ink compositionmust be leveled and form uniform film before the evaporation of thehighly-volatile second non-aqueous solvent. If the initial viscosity isexcessively high, it is difficult to level the ink composition and thusto coat the ink composition on the roller.

By applying the conductive metal ink composition for the roll printingmethod, the fine conductive pattern can be easily formed on thesubstrate. Particularly, the ink composition includes specific organicsilver complex and thus, forms the conductive pattern with an excellentconductivity.

Therefore, the conductive metal ink composition can be printed on thesubstrate, for examples, a glass substrate according to the rollprinting method, to form the conductive pattern, or preferably theelectrode element of flat display element.

In accordance with an embodiment of the present invention, there isprovided a method of preparing the conductive pattern. The method offorming a conductive pattern comprises the steps of: coating theconductive metal ink composition on a roller; forming a pattern of theink composition corresponding to the conductive pattern on the roller bycontacting the roller with a printing cliché which has an intagliopattern corresponding to the conductive pattern; transferring thepattern of the ink composition on the roller onto a substrate; andsintering the transferred pattern on the substrate.

In the method of forming the conductive pattern, the term, “cliché”means the rough(

) plate which is used to form conductive pattern in a desired shape byapplying the ink composition on the roller. The intaglio patterncorresponding to the conductive pattern can be formed on in the cliché.

Referring to the attached drawings, the method of forming the conductivepattern according to the embodiment of the present invention will bedescribed step by step. FIG. 1 is a schematic drawing to briefly showthe steps of preparing the conductive pattern according to the rollprinting method.

Firstly, the homogeneous ink composition can be prepared by mixing thecomponents and agitating. To remove the impure materials and to formuniform conductive pattern, the ink composition can be further filtered.

Sequentially, the conductive ink composition (22) is coated on theroller (20). The outer surface of the roller (20) can be covered withblanket (21) which may comprise polydimethysiloxane (PDMS). PDMS can beproperly used as blanket (21), because it has better adhesiveness, andelastic, transforming and transferring properties than other polymers.The blanket (21) can be coated by the conductive ink composition whichcan be provided with an inflow hole (10) of an apparatus of providingthe ink composition. At this time, as the second non-aqueous solventbegins to evaporate, the viscosity of ink composition (22) increasessharply.

After coating the ink composition (22) on the blanket (21), the patternof the ink composition corresponding to the conductive pattern is formedon the roller by contacting the roller with a printing cliché having theintaglio pattern corresponding to the conductive pattern.

That is, the cliché (30) removes selectively the ink (32) which need notfor pattern formation, by contacting with the blanket (21) coated withthe ink composition (22), resulting in preparing a desired pattern onthe roller corresponding to the conductive pattern. To do so, the cliché(30) has the intaglio pattern corresponding to the conductive pattern onits surface contacting with the blanket (21). Only protruding part (31)of the cliché (30) contacts with the ink composition (22) on the blanket(21), and transfers the ink (32) to the protruding part (31), resultingin removing the ink which is not required to form the conductivepattern.

After forming the pattern of ink composition on the roller, the patternis transferred to the substrate. The pattern of ink composition istransferred to the substrate (40) by contacting the blanket (21) whichthe pattern of ink composition is formed on, with the substrate (40) toform desired pattern (41) on the substrate (40).

After transferring step, the conductive pattern on the substrate can beformed by sintering. The sintering step can be performed under theproper conditions that are dependent on the kind of desired conductivepattern. For example, in case that the conductive pattern is used for anelectrode pattern of flat display device, the sintering step can becarried out at about 300 to 600° C. for about 5˜50 minutes, particularlyat about 400 to 480° C. for 10 to 40 minutes.

According to the method of preparing the conductive pattern using theroll printing method, the conductive pattern can be formed rapidly andsimply on the substrate, compared with photolithography used in theprior art. As the ink composition is applied to the roll printingmethod, it is easy to form the fine conductive pattern with an excellentconductivity, for example, the electrode pattern of flat panel displaydevice.

Advantage Effect

As described above, the present invention provides a conductive metalink composition which can be properly applied for roll printing processto form a conductive pattern. In addition, the conductive pattern withexcellent conductivity can be prepared by using the conductive metal inkcomposition.

Therefore, by applying the conductive metal ink composition to the rollprinting method, it is possible to prepare a fine conductive pattern,for example, a fine electrode pattern of flat panel display element.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic drawing showing a method of preparing theconductive pattern according to the roll printing method.

FIG. 2 is a microscopic image of the conductive pattern obtained inExample 1.

FIG. 3 is a SEM image of fine structure of the conductive patternobtained in Example 1.

FIG. 4 is a SEM image of fine structure of the conductive patternobtained in Comparative Example 1.

EXAMPLES

The present invention is further explained in more detail with referenceto the following examples. These examples, however, should not beinterpreted as limiting the scope of the present invention in anymanner.

Example 1

Conductive Metal Ink Composition and Formation of Conductive Pattern

8.57 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin as a phenol polymer were mixed and agitated for 12 hours. 5 wt %of silver (Ag)(hexanoate)(diethanolamine)₂ on the basis of weight ofsilver nanoparticle was added to the resulting solution, agitated for 12hours, and filtered with a filter having a pore size of 1 μm to preparethe ink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 4.02 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Example 2

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin as a phenol polymer were mixed and agitated for 12 hours. 5 wt %of silver (Ag)(hexanoate)(diethanolamine)₂ on the basis of weight ofsilver nanoparticle was added to the resulting solution, agitated for 12hours, and filtered with a filter having a pore size of 1 μm to preparethe ink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 3.63 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Example 3

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 12 hours. 5 wt % ofsilver (Ag)(propionate)(diethanolamine)₂ on the basis of weight ofsilver nanoparticle was added to the resulting solution, agitated for 12hours, and filtered with a filter having a pore size of 1 μm to preparethe ink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 2.97 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Example 4

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 12 hours. 5 wt % ofsilver (Ag)(stearate)(diethanolamine)₂ on the basis of weight of silvernanoparticle was added to the resulting solution, agitated for 12 hours,and filtered with a filter having a pore size of 1_(i)m to prepare theink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 3.29 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Example 5

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 12 hours. 5 wt % ofsilver (Ag)(hexanoate)(2-methoxyethylamine)₂ on the basis of weight ofsilver nanoparticle was added to the resulting solution, agitated for 12hours, and filtered with a filter having a pore size of 1 μm to preparethe ink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 2.68 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Example 6

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 12 hours. 5 wt % ofsilver (Ag)(hexanoate)(2-methylaminoethanol)₂ on the basis of weight ofsilver nanoparticle was added to the resulting solution, agitated for 12hours, and filtered with a filter having a pore size of 1 μm to preparethe ink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 2.83 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Example 7

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 12 hours. 5 wt % ofsilver (Ag)(hexanoate)(triethanolamine)₂ on the basis of weight ofsilver nanoparticle was added to the resulting solution, agitated for 12hours, and filtered with a filter having a pore size of 1 μm to preparethe ink composition. The initial viscosity of the ink composition wasmeasured according to the following method, and was 4.05 cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Comparative Example 1

Conductive Metal Ink Composition and Formation of Conductive Pattern

6.67 g of silver nanoparticle having an average diameter of 50 nm, 2.3 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 10 g of butylcellosolve (vapor pressure 0.76 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenolic polymer were mixed and agitated for 12 hours. Theresulting solution was filtered with a filter having a pore size of 1 μmto prepare the ink composition. The initial viscosity of the inkcomposition was measured according to the following method, and was 2.93cPs.

The PDMS blanket of roller was coated with the ink composition, and wascontacted with cliché having an intaglio pattern corresponding to thedesired conductive pattern to form the pattern of ink composition on theroller. Then, the pattern on the roller was transferred onto the glasssubstrate by contacting the roller with the glass substrate, andsintered at 450° C. for 30 minutes in thermal furnace to obtain theconductive pattern.

Reference 1:

Preparation of an Ink Composition with High Viscosity

7.5 g of silver nanoparticle having an average diameter of 16 nm, 2.6 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 7.7 g ofethanol (vapor pressure of 59.3 torr at 25° C.), 9.9 g of propylcellosolve (vapor pressure 0.975 torr at 25° C.), 0.8 g ofN-methylpyrrolidone (vapor pressure of 0.375 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 12 hours. Theresulting solution was filtered with a filter having a pore size of 1 μmto prepare the ink composition. The initial viscosity of the inkcomposition was measured according to the following method, and was 128cPs.

Reference 2:

Preparation of an Ink Composition with High Viscosity

6.0 g of silver nanoparticle having an average diameter of 16 nm, 6.1 gof methyl cellosolve (vapor pressure of 6.2 torr at 25° C.), 11.4 g ofpropyl cellosolve (vapor pressure 0.975 torr at 25° C.), 0.5 g ofN-methylpyrrolidone (vapor pressure of 0.375 torr at 25° C.), 0.2 g ofpolydimethylsiloxane surfactant, and 0.7 g of phenol aldehyde novolacresin of phenol polymer were mixed and agitated for 60 hours. Theresulting solution was filtered with a filter having a pore size of 1 μmto prepare the ink composition. The initial viscosity of the inkcomposition was measured according to the following method, and was 34cPs.

Test Example 1

Measurement of Initial Viscosity of the Conductive Ink Composition

The initial viscosity of the ink compositions obtained in Examples 1 to7, Comparative Example 1, and References 1 and 2 were measured by usingBrookfield viscometer and was shown as above.

Test Example 2

Test of Conductive Pattern Properties

The conductive pattern obtained in Example 1 was observed with a lightmicroscope (Nikon, Eclipse 90i) and the microscopic image was shown inFIG. 2. FIG. 2 confirmed that the conductive pattern with line width ofabout 10 μm was satisfactorily formed by using the ink composition ofExample 1. On the other hand, the ink composition having an initialviscosity of higher than 10 cPs obtained in References 1 and were noteven able to be coated on the roller.

Before and after sintering the conductive patterns prepared from the inkcompositions of Example 1 and Comparative Example 1, the sinteredpatterns were observed with an electron microscope (HITACHI, S-4800) andshown in FIGS. 3 and 4. FIGS. 3 and 4 confirmed that the conductivepattern of Example 1 included the conductive metal component (silver) athigher density than that of Comparative Example 1.

The conductivity of each conductive pattern obtained in Examples 1, 2, 5to 7 and Comparative Example 1 was tested by measuring the specificresistance of the conductive pattern. The specific resistance wascalculated by multiplying the sheet resistance measured by 4 point probe(Mitsubishi chemical, MCP-T600) and the thickness measured by usingalpha step. The obtained specific resistance was represented in Table 1.

TABLE 1 Specific Resistance (μΩ · cm) Example 1 9.80 Example 2 4.50Example 5 17.29 Example 6 13.31 Example 7 15.92 Comparative Example 179.60

Referring to Table 1, the conductive patterns of Examples 1, 2, 5, 6 and7 showed very low specific resistance and excellent conductivity due tothe inclusion of organic silver complex. However, it was confirmed thatthe conductive pattern of Comparative Example 1 had high specificresistance and low conductivity.

The invention claimed is:
 1. A conductive metal ink compositioncomprising a conductive metal powder; an organic silver complex where anorganic ligand including amine group and hydroxyl group binds with asilver (Ag) salt of aliphatic carboxylic acid; a non-aqueous solventcomprising a first non-aqueous solvent having a vapor pressure of 3 torror lower at 25° C. and a second non-aqueous solvent having a vaporpressure of higher than 3 torr at 25° C.; and a coatability improvingpolymer.
 2. The conductive metal ink composition of claim 1, wherein thecomposition is used for forming a conductive pattern, by being printedon a substrate with a roll-printing process.
 3. The conductive metal inkcomposition of claim 2, wherein the composition is used for forming anelectrode of flat panel display device.
 4. The conductive metal inkcomposition of claim 2, wherein the composition has an initial viscosityof 20 cPs or lower.
 5. The conductive metal ink composition of claim 1,wherein the conductive metal powder comprises at least one metal powderselected from the group consisting of silver (Ag), copper(Cu), gold(Au),chrome(Cr), aluminum(Al), tungsten(W), zinc(Zn), nickel(Ni), iron(Fe),platinum(Pt) and lead(Pb).
 6. The conductive metal ink composition ofclaim 1, wherein the conductive metal powder has an average particlediameter of 1 to 100 nm.
 7. The conductive metal ink composition ofclaim 1, wherein the silver salt of aliphatic carboxylic acid isselected from the group consisting of the silver salts of C2-C20 primaryfatty acid and C2-C20 secondary fatty acid, and the organic ligand isselected from the group consisting of primary, secondary, tertiary, andquaternary amines substituted with an alcohol group.
 8. The conductivemetal ink composition of claim 1, wherein the organic ligand binds withthe silver (Ag) salt of aliphatic carboxylic acid at which an equivalentratio of the organic ligand to the aliphatic carboxylic acid is 2:1 inthe organic silver complex.
 9. The conductive metal ink composition ofclaim 1, wherein the first non-aqueous solvent comprises at least onenonvolatile solvent selected from the group consisting of alcohol-basedsolvent, glycol-based solvent, polyol-based solvent, glycol ether-basedsolvent, glycol ether ester-based solvent, ketone-based solvent,hydrocarbon-based solvent, lactate-based solvent, ester-based solvent,aprotic sulfoxide-based solvent, and nitrile-based solvent, which have avapor pressure of 3 torr or lower at 25° C.
 10. The conductive metal inkcomposition of claim 1, wherein the second non-aqueous solvent comprisesat least a volatile solvent selected from the group consisting ofalcohol-based solvent, glycol ether-based solvent, glycol etherester-based solvent, ketone-based solvent, hydrocarbon-based solvent,lactate-based solvent, ester-based solvent, aprotic sulfoxide-basedsolvent, and nitrile-based solvent, which have a vapor pressure ofhigher than 3 torr at 25° C.
 11. The conductive metal ink composition ofclaim 1, wherein the coatability improving polymer comprises at least anadhesive polymer selected from the group consisting of epoxy-basedpolymer, phenol-based polymer, alcohol-based polymer, ethylene vinylacetate, rosin-based polymer, styrene-butadiene-styrene-based polymerand polyester-based polymer.
 12. The conductive metal ink composition ofclaim 1, wherein the composition comprises, 15 to 30 wt % of theconductive metal powder; 5 to 70 wt % of the first non-aqueous solvent;10 to 74 wt % of the second non-aqueous solvent; and 0.1 to 5 wt % ofthe coatability improving polymer, on the basis of total weight of othercomponents in the composition except for the organic silver complex, and0.1 to 5 parts by weight of organic silver complex on the basis of 100parts by weight of the conductive metal powder.
 13. The conductive metalink composition of claim 12, wherein the composition further comprises0.01 to 4 wt % of surfactant, on the basis of total weight of othercomponents in the composition except for the organic silver complex.